Means for avoiding disturbances in the reception of electric oscillations



Jan'. 24, 1939. 2,144,995

MEANS FOR AVOIDING DISYTURBANCES IN` THE RECEPTION OF ELECTRIC OSCILTJATIONS PuLvARl-PULVERMAC'HER Filed OCT.. 2, 1935 3 Sheets-Sheet l I IIIIII VIII' Ve/v T'OFT' 9" MW @95.

Jan. 24, 1939. K. PuLvARl-PULVERMACHER 2,144,995

MEANS FORV VOIDNGl DISTURBANCES IN THE RECEPTION OF ELECTRIC OSCILLATIONS Filedoct. 2, 1935 s sheets-Sheet 2 24, 1939- K. PULvARx-ULVERMACHER 2,144,995

MEANS FOR AVOIDING DISTURBANCES IN THE RECEPTION OF ELECTRIC OSCILLATIONS Filed Oct. 2, 1935 3 Sheets-Sheet 5 Patented Jan. 24, 1939 UNITED STATES PATENT oFFICE .MEANS FOR AVOIDING DISTURBANCES IN THE RECEPTION O-F ELECTRIC OSCILLA- TIONS Karl Pulvri-Pulvermacher, Budapest, Hungary Application October 2, 1935, Serial No. 43,254 In Austria October 8, 1934 Claims.

This invention relates to an arrangement for the reception of modulated alternating currents,4 more particularly speech currents in which disturbing voltages due to atmospheric influences or the like are avoided.

It has already been proposed to use for this purpose arrangements which would limit the intensity or the voltage of the current to be amplied. Thus, for instance, arrangements are known in which a glow lamp is arranged in par@- allel with the alternating current circuit, for instance, in parallel with the transformer through which the speech frequencies are transmitted, which glow lamp responds to a voltage of a definite value therebypreventing the further increase in voltage in the circuit to be protected. One disadvantage of these arrangements lies in the fact that they respond only to a definite maximum! voltage so that disturbing voltages which arise, for instance during the reception of Weak music or speech currents, are not at all suppressed' or only partly according as to whether their amplitude, which may be a multiple of the amplitude to be received, is smaller or greater than the limiting voltage adjusted to a fixed value on the protecting device.

The frequency and the amplitude of the disturbing voltages are generally substantially greater than the frequency and the amplitude of "a voltage, the curve of which corresponds to the enveloping curve of the modulated alternating current or speech current to be received.

The general use of the devices for the purpose,

ing voltages is removed by cutting off the higher' frequencies, is based on this idea.

According to the invention, the modulated electric oscillations are supplied to an arrangement limiting the voltage, which arrangement cuts off all the voltages Which are higher than the individual voltage amplitudes of the enveloping curvel of the oscillations to be received. By the oscil-, lation or amplitude to be received, I understand the modulated alternating currents, music or speech currents which have been freed of the disturbing voltages.

The invention is illustrated diagrammatically in the accompanying drawings, in which Figure 1 is an explanatory diagram and Figures 2, 3, 4, 5 6 and 7 show different arrangements of connections.

If speech or music currents are registered together with the atmospheric disturbances by means of an oscillograph, a curve, such as shown in Figure 1, is obtained, wherein the disturbing voltages s can clearly be seen.

According to the invention, the apparatus is voltage constitutes the enveloping curve u of the oscillations e to be received and that this voltage is applied to an electric discharge tube which acts as a voltage limiter. As compared with the known limiting arrangements, the substantial advantage is thereby secured that the disturbing voltages are always substantially completely cut cil with any small value of the voltages to be received, since the enveloping curve u, representing the limiting voltage, conforms to the upper and lower values of the voltage to be received.

According to the invention, the voltage u, acting as a limiter, is obtained by this, that a portion of the oscillations to be received and which are already rectified so that they can be received, that is to say freed of the carrier frequency, are again rectified before or after amplification and then supplied to a suitable filter circuit. The production of the enveloping curve by means of such lter circuits is known in the talking film industry, wherein they are used for the so-called noiseless sound recording. A portion of the disturbing voltages may be separated in a known manner before the rectication from the alternating current voltages to be rectied. The pulsating continuous current voltage so obtained corresponds to the said enveloping curve u. Thisl voltage is applied as a negative voltage bias to an electric discharge tube connected with the receiving circuit, which discharge takes place as soon as a disturbing voltage arises in the receiving circuit, whereby this voltage is consumed, for instance in an impedance, without reaching the amplier.

Figure 2 illustrates, by way of example, an arrangement according to the invention. An impedance I2 is connected in series with the secondary winding I I of the transformer I, which impedance I2 is connected to the grid of the amplifying valve I3. The output circuit of the amplier I3 contains, as usual, the primary winding I4 of the transformer II and the source of voltage I5. A portion of the outgoing oscillations is supplied through the secondary winding I6, the rectifying circuit I'I and the lter circuit I8 t0 the resistance I9 which acts as a potentiometer. The latter is connected through the sliding contact 20 to the secondary winding of the transformer I and is connected to the cathode of an Y electric discharge tube 2|, which is in parallel with the secondary winding II, the polarities being as indicated in the drawings.

The alternating current voltages which arise in the circuit of the coil II reach the negatively biased grid of the amplifier I3; a portion of the amplied oscillations is rectified at I'I, is suitably filtered in the circuit I8 and the continuous current voltage so obtained, the amplitude and enveloping curve of which correspond to the speech current acts on the impedance I9. The sliding contact is so adjusted that the voltage acting between the same and the point 22 is a few per cent higher than the voltage to be received in the coil Il. As long as no disturbing voltages arise in the circuit E the cathode of the discharge tube 2| is more positive than the anode so that a discharge cannot take place. However, if there is a disturbing voltage which generally is substantially higher than the above-mentioned continuous current voltage on the potentiometer I9, the valve responds immediately and, owing to the short circuit which is thereby produced, the disturbing voltage breaks down in the impedance I2 or only a small fraction of this Voltage reaches the amplifier according to the dimensions of the impedance. Actually in this way all the voltages are cut off which are higher than the voltage of the continuous current which is proportional to the alternating current to be received.

The electric discharge tube, acting as a voltage limiter, may be connected directly or indirectly through other electrical elements to the receiving circuit.

As will be seen in the arrangement according to Figure 2, disturbing voltages are cut off only on one side of the abscissae (in one half period). If the signs of the voltages on the winding II and potentiometer are opposite the valve 2| responds to the disturbing voltages. If the signs are of the same sense, the voltages to be received (for instance, speech or music currents) are added together including the disturbing voltages; the negative voltage bias of the valve 2I increases and a discharge cannot take place therein.

Complete protection is obtained by the arrangement shown in Figure 3. Two discharge tubes 2|c and 2lb and two potentiometers I9a and I9b form a bridge, the one valve being connected with its anode and the other one with the cathode to the impedance I2 and over the same to the same end of the winding Il. It will be clear that according to the direction of the voltage applied to the coil II in the one half period, the valve 2Ic and, in the other half period, the valve 2lb, will respond when disturbing voltages arise therein. The rectifying circuit I1 and the filter circuit I8 are properly connected to the pctentiometers I9a, I 9b in the same way as in the construction illustrated in Figure 2.

Instead of a vacuum valve (diode), also a gas-lled valve may be used as the discharge tube. The usual electron discharge Valve responds immediately to any voltage which is more positive than the cathode. The glow discharge valve responds only to a voltage which is higher than the starting voltage of the valve. In order to ensure that the glow discharge valve will act in the same way as the electron valve in the arrangement referred to, according to the invention the glow discharge 23, shown in Figure 4, is connected to a source of voltage 24, the voltage of which is such that it lies in the proximity of the starting voltage of the valve 23. When two glow discharge valves are employed, the connections are effected in a similar way.

The circuit Il need not be coupled to the output circuit of the amplifier. The oscillations to be rectied and ltered may be obtained from the circuit E by suitable tapping.

In the arrangement described the electric discharge tube acts in the same way as a controllable optical shutter by regulating the voltage passage in the arrangement in dependence upon the amplitudes to be received, that is to say the amplitudes of the enveloping curve (Figure 1). Preferably, a constant bias voltage is applied to the discharge tube in order to avoid the complete closure of the shutter, in which case theoretically the same would not allow any voltage to pass through. The electric discharge tube may also consist of a discharge valve with one or more grids, in which case the voltage bias, as Well as the shutter control voltage, are applied to one or more grids. By shutter control voltage, I understand the continuous current voltage acting on the impedance IS and which is proportional to the voltage received.

The shutter voltage may also consist of two voltages which are combined together according to the received current amplitudes, rectied but connected in opposite directions and which are so produced that the received oscillations are split by means of a frequency filter into high and low frequency components and which, after having been separately rectied, are supplied in opposite directions to the potentiometer I9 in Figure 2. In this case the rectied voltage of the high frequency component acts merely as a voltage closing the electric amplitude shutter.

When an amplifier is used for the reception, the discharge tube 2| may also be built in the amplifying valve. It is also possible to use as electric discharge tube a valve having one or more grids, wherein the constant Voltage bias and the shutter controlling voltage is or are supplied to the grid or grids of the valves.

Such a constructional form is shown in Figure 7, in which 25 indicates a two-grid tube with a cathode 26 and an anode 21. The constant preliminary voltage Eg is applied to the grid 28 and the blocking Voltage Eb to the grid 29. The reference characters I, II and III indicate the same parts as in Figure 3.

Instead of the discharge gap 2|, use may be made of any kind of rectifier.

Such an arrangement is shown in Fig. 6 in which the various references refer to the same parts as in Fig. 2. The discharge tube 2I in this case has a grid connected to the sliding contact 20 of the potentiometer. 'I'he secondary winding of the transformer is connected in parallel with the tube 2|.

Instead of using batteries, as shown in the various figures, use may be made in a known manner of sources of voltages which are known in weak current electrotechnics for producing a voltage drop (for instance, a potentiometer or the like).

The arrangement hereinbefore described may also be used with advantage in heavy current electrotechnics as a protection against undesirable voltage waves, in which case the electric discharge tube may consist of Thyratron valves of large output.

The impedance of the diierent circuits may consist of any desired complex resistance, the inductive capacitative or ohmic components of which are chosen according to the purpose in View but which must be connected together in relations corresponding to the special purpose.

What I claim is:

1. Apparatus for receiving electrical oscillations free of disturbances, comprising a receiving circuit, at least one electric discharge tube connected to the receiving circuit, means for effecting a first rectification to free the received oscillations of the carrier frequency, means for effecting a second rectication, a device for separating disturbing voltages due to atmospheric influences prior to the second rectification, and means for applying the twice rectified oscillations to said electric discharge tube in the form of a voltage bias, the curve of which constitutes the enveloping curve of the amplitudes of the received oscillations, whereby disturbing voltages the amplitudes of which are higher than the amplitudes of the received oscillations are removed through the electric discharge tube.

2. Apparatus for receiving electrical oscillations free of disturbances as claimed in claim 1 in which the means for applying the twice rectied oscillations to the electric discharge tube comprises a iilter circuit and an impedance connected in series with the electric discharge tube in the receiving circuit.

3. Apparatus for receiving electrical oscillaktions free of disturbances comprising a receiveare maar ing circuit, two electric discharge tubes, means for effecting a rst rectification to free the received oscillations of the carrier frequency, means for eifecting a second rectification, means for separating disturbing voltages resulting from atmospheric influences prior to the second rectification, means for applying the twice rectified oscillations to the two electric discharge tubes in the form of a voltage bias, the curve of which constitutes the enveloping curve of the amplitude of the received oscillations, whereby disturbing voltages of amplitudes which are higher than amplitudes of the received oscillations are removed through the electric discharge tube, the means for applying the oscillations to the tubes including two impedances connected with the two electric discharge tubes in the form of a Wheatstone bridge and the receiving circuit and the means ,for eiecting the rectiiication lying in the arms of the bridge.

4. Apparatus as claimed in claim 1 characterized by a constant bias voltage impressed on the electric discharge tube.

5. Apparatus as claimed in claim 1 characterized by the feature that a multi-grid valve is employed as the electric discharge tube, a constant bias voltage and a grid control voltage being supplied to the grids of this valve.

KARL PULvRI-PULVERMACHER. 

